The transition metal chemistry of quinuclidinone-containing ligands—VII[1]

J. inorg, nucl. Chem., 1974,Vol. 36, pp. 1235 1238.Pergamon Press. Printed in Great Britain.

THE TRANSITION METAL CHEMISTRY OF QUINUCLIDINONE-CONTAINING LIGANDS--VII[1] COBALT(II) AND NICKEL(II) THIOCYANATE COMPLEXES OF

2.-(N-MORPHOLINYLMETHYL)-3-QUINUCLIDINONE RICHARD C. DICKINSON and GARY J. LONG* Department of Chemistry, University of Missouri-Rolla, Rolla, Missouri 65401 (Received 17 July 1973)

A~traet--Complexes of cobalt(lI) and nickel(II) thiocyanate with 2-(N-morpholinylmethyl)-3-quinuclidinone, MQN, were prepared by adding the metal salt to the ligand in alcoholic solutions. The resulting complexes had the stoichiometry Co(MQN)(NCS)2. C2H5OH and Ni(MQN)(NCS)2. CH3OH. A study of their magnetic and i.r. and electronic spectral properties has indicated that these complexes contain metal ions in octabedral coordination sites.

INTRODUCTION

IN AN investigation of the coordinating ability of quinuclidinone-containing ligands, we have shown that 2-(N-morpholinylmethyl)- 3-quinuclidinone, MQN, forms complexes of the general type M(MQN)X2

MQN

(where M = Co, Ni, Fe, and X = CI, Br, I)[2]. These complexes contain the metal ion in a pseudotetrahedral coordination geometry as determined by their spectral and magnetic properties. We believe that M Q N has a preference for pseudotetrahedral coordination due to the bulkiness of the quinuclidinone group and the rigid five membered ring formed by the chelate ring with the metal ion. In continuing the investigation of this ligand, we have prepared the Co(II) and Ni(II) thiocyanate complexes, and we report their preparation and spectral and magnetic properties in this paper.

and filtered. To this hot filtrate was added a hot solution of 1-50 g of MQN (0.007 mole) in 25 ml of ethanol. The solution was then cooled to room temperature and filtered to remove a flocculent precipitate which formed. About 100 ml of cyclohexane was added to the filtrate to promote crystallization. The walls Of the container were scratched, and a purple solid formed upon standing. The product was collected by filtration and was washed using ethanol and ether. After drying in vacuo over P40~o for several days, the product was a light purple, crystalline powder. Anal. Calcd. for CoCI6H26N40352 : C, 43.14; H, 5.88; N, 12.58. Found: C, 43.09; H, 6,06; N, 12.61. Ni(MQN)(NCS)2. CH3OH. A sample of Ni(NCS)2 weighing 1.15 g (0.007 mole) was dissolved in 50 ml of hot anhydrous methanol and the mixture cooled and filtered. A mixture of 1.50 g of MQN (0.007 mole) in 25 ml ofanhydrous methanol was added dropwise with stirring to the metal salt solution and 50 ml of anhydrous diethyl ether added to promote crystallization. After stirring overnight, I00 ml of ether was added and the mixture refrigerated and filtered. The product was a light green powder and was dried over P4Olo in vacuo for several days. Anal. Caled. for NiC15H24N,~O3S2 : Ni, 13.62; C, 41,78; H, 5.61; N, 12.99. Found: Ni, 13.78; C, 41.62; H, 5.78; N, 12.76. Methods of study

EXPERIMENTAL The ligand 2-(N-morpholinylmethyl)-3-quinuclidinone, MQN, was prepared by previously described methods[2] using quinuelidinone obtained from the Aldrich Chemical Company. Preparation of the complexes

Co(MQN)(NCS)2. C2HsOH. A mixture of 1.16 g of Co(NCS)2 (0.007 mole) in 5 ml of ethanol was heated to boiling * Author to whom correspondence should be addressed.

Electronic absorption spectra were recorded using a Cary 14 Spectrophotometer. Spectra of the complexes in the solid phase were obtained by mulling the powder with KeI-F No. 90 fluorocarbon grease and spreading the mull between two thin quartz plates. Solution electronic absorption spectra were obtained using spectral grade solvents and matched quartz sample ceils of various path lengths. I.R. spectra in the range 4000-400 cm-I were recorded using a Perkin-Elmer 337 grating spectrophotometer and spectra in the range 800-200 cm-I were obtained with a Beckman IR-12 grating spectrophotometer. In the lower energy range, samples were ground with freshly-dried cesium iodide and pellets were prepared by the standard method.

1235

1236

RICHARDC. DICKINSONand GARYJ. LONG Table 1. Infrared spectral data for cobalt(lI) and nickel(II) thiocyanate complexes* Compound

Co(MQN)(NCS)z. C2H~OH

C-N stretch C-S stretch N-C-S bend M-NCS stretch O-H stretch

Ni(MQN)(NCS)2 . CHaOH

2110 s; 2070 s; 2025 sh 780 w 490 m 280 s,br 3225 br

2130 s; 2090 s 480 m 290 s 3400 br

* Abbreviations : s, strong; m, medium; w, weak ; sh, shoulder; br, broad. Frequencies are expressed in cm - 1 Potassium bromide was used in the higher energy infrared range. Magnetic susceptibility measurements were obtained at various temperatures on a standard Gouy balance. The system was calibrated[3] using HgCo(NCS),~and the sample temperature was measured using a copper-constantan thermocouple. Diamagnetic corrections to the total susceptibilities were made using Pascal's constants. Nickel analyses were performed in the author's laboratory using EDTA titrations. Carbon, hydrogen, and nitrogen elemental analyses were performed by Galbraith Laboratories, Knoxville, Tennessee. RESULTS AND DISCUSSION

The thiocyanate ligand is known to coordinate in different modes[4], and i.r. spectroscopy has proved an effective method of distinguishing between these modes [5]. Complexes containing N-bonded thiocyanate exhibit a C - N stretching frequency generally in the range 2040-2080 cm -1, and the S-bonded ligand exhibits this vibration in the range 2080-2120 cm-1. The C-S stretching frequency is found in the general regions 780-860 c m - a and 690--720 era- 1 for terminal, N-bonded and S-bonded thiocyanate groups, respectively; similarly, the N--C-S bending mode occurs in the ranges 450-490 c m - 1 and 400-440 era- 1. A number of cobalt and nickel thiocyanate complexes have been reported where the C - N stretching frequencies are 30-60 c m - 1 (or more) higher than in the case of terminal thiocyanate groups[6,7]. This is reportedly due to the presence of M-NCS--M bridges. Furthermore, it has been suggested that extensive splitting of the band corresponding to the anti-symmetric stretch occurs in complexes containing both terminal and bridging thiocyanates[7].

Examination of the i.r. spectra ofCo(MQN)(NCS)2 .C2HsOH and Ni(MQN)(NCS)2. CH3OH provides the information given in Table 1. The cobalt complex shows definite splitting of the C - N stretching mode into two bands of almost equal intensity, due to the presence of both terminal and bridging thiocyanates. The bands at 2070, 780 and 490 cm-1 indicate that the terminal ligands are N-bonded. The coordination sphere is completed by a coordinated molecule of ethanol, the solvent in which the complex was prepared. The O--H stretching frequency for ethanol is observed[8] as a broad band at 3660 cm -1 and is found at lower frequencies in coordinated ethanol. In the cobalt complex, the v(O-H) mode corresponds to a broad band centered around 3225 cm-1. No other bands, except those present in the spectrum of the ligand are observed. The presence of bridging thiocyanate implies a dimeric structure, and in the absence of an X-ray crystallographic study, this structure is tentatively proposed. One of several possible dimers is shown in Fig. 1. This structure requires an octahedral ligand field and this was confirmed by analysis of electronic absorption spectra and magnetic properties. There are three spin-allowed d-d transitions predicted for a cobalt(II) ion in a regular octahedral field represented by h, 4TIg(F)~ 4T2g(F); v2, ~Tlg(F)~ 4A2g(F); v3, 4Tlg(F)--* 4Tlg(P). Band positions corresponding to these transitions are presented in Table 2 with the calculated parameters Dq and B. The octahedral coordination sphere of the cobalt ion in Co(MQN)(NCS)2. C2HsOH is distorted as judged by the band

2000

Wavelength, I000

rn H500

} .Q < SCN '-

}

R-IO~ H

NCS

I

RJ O s H

Fig. I. Proposed structure of Co(MQN)(NCS)2 . C 2 H s O H and Ni(MQN)(NCS)2. CHaOH.

5

I

I0 Frequency,

15 crn -I x l G 3

--

20

Fig. 2. Mull electronic absorption spectrum of Co(MQN)NCS) 2 . C 2 H s O H .

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Chemistry of quinuclidinone-containingligands--VI1 Table 2. Electronic spectral data for cobalt(ll) and nickel(II) thiocyanate complexes* Compound Co(MQN)(NCS)2 . C2HsOH Ni(MQN)(NCS)2. CHaOH

Co(MQN)(NCS)2. CzH~OH Ni(MQN)(NCS)2 . CH3OH

Solvent

Symmetry

vI , cm- 1

v2 , cm-

Mull Acetone Mull DMF

Octahedral Tetrahedral Octahedral Octahedral

7550sh; 9215

18,180 6370 ( I0) ; 8200 (35) ; 10,700 (20) 15,300; 12,230 sh 15,450(13); 16,165 sh; 17,000 sh; 13,000 sh

Mull Acetone Mull DMF

v3, cm- 1 19,230; 20,875 15,450 (450); l 6,025 sh ; 17,860 (150); 18,520 sh 25,500 sh 25,560 (25)

9240 9100(10)

Dq, cm J 970-~ 490~ 970 955

B, cm 844 628 835 820

* Abbreviations : sh, shoulder. Molar extinction coefficients given in parentheses. DMF is dimethylformamide. f Values of Dq were calculated from values of v2 and v3 where v3 was taken a~ the simple average of components assigned v3. Value of va taken as center of band at half maximum ; v2 taken as 8200 cm- 1.

to

splitting observed in the mull spectrum presented in Fig. 2. The transition to the 4Tlg energy level (v3) in regular octahedral symmetry is triply degenerate and this degeneracy is lost in lower symmetries. On this basis, the bands at 19,230 and 20,875 c m - 1 are assigned as components of v3, and the band at 9215 cm-~ with its shoulder at ca. 7550 e m - ~ is assigned to components of v~. The vz transition corresponds to the band located at 18,180cm -1. Magnetic properties are given in Table 3. The magnetic moment of 4.38 B.M. is somewhat lower than expected[9] for cobalt(II) in octahedral symmetry.However, the temperature dependence of the moment is anticipated for this symmetry. The dimeric cobalt thiocyanate complex is decomposed in solution ; in acetone, the product is distinctly tetrahedral as judged by the solution absorption spectrum and is most likely Co(MQN)(NCS) 2 monomers. The solution absorption spectrum is very similar to those of the analogous halide complexes[2] and is shown in Fig. 3. Bands located at 6370, 8200, and 10,700 c m - t are associated with the v2 transition in pseudotetrahedral symmetry, The bands at 15,450, 16,025(sh), 17,860, and 18,520(sh) c m - 1 are components of the v3 transition in pseudotetrahedral symmetry. Values calculated for Dq and B are 490 and 628 c m - 1, respectively, and are typical for cobalt(II) in this coordination geometry. The complex Ni(MQN)(NCS)2. CH3OH contains octahedrally coordinated nickeI(II) ion as determined Table 3. Magnetic susceptibility results Compound

T ~(x106) /~eff (°K) (cgsunits) (B.M.)

Co(MQN)(NCS) z . C2HsOH MW = 445.5 zc = 253

130,0 295.0

16,380 8120

4.13 4.38

Ni(MQN)(NCS)2. CH3OH MW = 431.2 Z,- 241

122.0 167.0 291-0

10,130 7650 4480

3.14 3.20 3-23

=

from the mull absorption spectrum presented in Fig. 4, the calculated spectral parameters (Table 2), and the magnetic susceptibility data (Table 3). As in the case of the analogous cobalt(II) complex, the octahedral ligand field is apparently generated by thiocyanate bridges and coordinated solvent molecules. In the i.r. spectrum, splitting of the C - N stretching mode into bands of similar intensity at 2090 and 2130 c m - ~ indicates the presence of the bridging thiocyanate ligands. The band at 2090 cm-~ is in the range found for Sbonded thiocyanate, however, a band of medium intensity at 480 cm-1 suggests N-bonded terminal groups. Unfortunately, examination of the spectrum in the region 700-900 c m - 1 reveals no band unique to the thiocyanate complex when compared to spectra of free M Q N and the analogous halide complexes. A band of strong intensity at 290 c m - 1 is, however, unique to this complex and is assigned to the N i - N C S metalligand stretching frequency. This vibration has been reported[10] at 295 c m - 1 (strongintensity) in anhydrous nickel(II) thioeyanate. Evidently, the terminal thiocyanates are N-bonded. The molecules of methanol

20

~5

Woveleng'lh, J2 JlO 9

.~ x I(~3 5 5OO

so4o 20

~

[~

5

3oo~

] I0 Frequency,

I00

i5

20

cm-I x 105

Fig. 3. Electronic absorption spectrum of the cobalt(II) thiocyanate complex in acetone solution.

1238

RICHARD C. DICKINSON a n d GARY J. LONG

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,

REFERENCES

m~

Wavelength, tO00 r n

T

500 [

400 [

I

I

I

I

I0

15

20

25

F'requency,

c m -~ x ~0 -3

Fig. 4. Mull electronic absorption spectrum of Ni(MQN)(NCS)2 . CH3OH. acquired from the solvent are presumably coordinated to the central metal atom. We observed an O - H stretching frequency at 3400 c m - 1 in the complex as opposed to the free methanol v a l u e [ I l l of 3683 cm -1. Data pertaining to the infrared spectral properties of Ni(MQN)(NCS)2. C H 3 O H are given in Table 1. In the absence of crystallographic proof, we again suggest a structure like the dimer shown in Fig. 1. Acknowledgements--The financial assistance of the National Science Foundation (Grants GP-8653 and GY-6625) is gratefully appreciated.

1. Part VI ; G. J. Long and E. O. Schlemper, J. chem. Sac. (Dalton). Submitted. 2. R. C. Dickinson and G. J. Long, Inorg. Chem., In press. 3. B. N. Figgis and R. S. Nyholm, J. chem. Sac. 4190 (1958). 4. R. A. Bailey, S. L. Kozak, T. W. Michelson and M. N. Mills, Coord. Chem. Rev. 6, 407 (1971); A. H. Norbury and A. I. P. Sinha, Q. Rev. chem. Sac. 24, 69 (1970); J. L. Burmeister, Coord. Chem. Rev. 3, 225 (1968); ibid. 1,205 (1966). 5. K. Nakamoto, Infrared Spectra of Inorganic and Coordination Compounds, 2nd Edn. Wiley-lnterscience, New York (1970). 6. W. J. Davis and J. Smith, J. chem. Sac. (A), 317 (1971); G. Contreras and R. Schmidt, J. inorg, nucl. Chem. 32, 127 (1970); S. C. Jain and R. Rivest, lnorg. Chim. Aeta 4, 291 (1970); R. S. Tobias, Inorg. Chem. 9, 2682 (1970) A. R. Davis, C. J. Murphy and R. A. Plane, lnorg. Chem. 9, 423 (1970); S. M. Nelson and J. RoaRers, Inorg. Chem. 6, 1390 (1967); L. Sacconi, I. Bertini, and F. Mani, lnorg. Chem. 6, 262 (1967); A. Sabatini and 1. Bertini, Inorg. Chem. 4, 959 (1965). 7. A. R. Davis, C. J. Murphy and R. A. Plane, Inorg. Chem. 9, 423 (1970); S. M. Nelson and J. Rodgers, lnorg. Chem. 6, 1390 (1967); J. Chatt and L. A. Duncanson, Nature, Land. 178, 997 (1956). 8. G. M. Barrow, J. chem. Phys. 20, 1739 (1952). 9. R. L. Carlin, Transition Metal Chem. 1, 1 (1965). 10. C. D. Flint and M. Goodgame, J. chem. Sac. (A), 442 (1970). 11. H. D. Noether, J. chem. Phys. 10, 693 (1942).